It’s hard to say SourceForge is in the wrong, given they’re subject to US law. On the other hand, I can’t say they’re in the right, because it does clearly violate the principles of open source/free software. Such situations are unfortunate, but the best solution seems to be ‘hope the law doesn’t come for you’. Not a long-term option.
You could argue then that they are in breach of the GPL on stuff they do use themselves. You can hardly take GPL source, modify it and refuse to distribute it to certain groups - wether this is your choice or a rule imposed by your country
A particular country's law takes precedence over the GPL.